1. Field of the Invention
This invention relates to a shutter for opening/closing the head access window of a magnetic disk cartridge. More particularly, this invention relates to an improved engagement means for the shutter.
2. Description of the Prior Art
In recent years development is moving ahead of magnetic disk cartridges consisting of a thin, small-diameter disk of magnetic recording media housed rotatably in a casing. These magnetic disk cartridges are provided with a magnetic head access window through which the recording media can be exposed for access by a magnetic head when the cartridge is being used. The casing is provided with a shutter for use with magnetic disk cartridges which can be slid to open the head access window for when the cartridge is being used or to close the window when the cartridge is not being used. This shutter is provided with an opening of the same shape as that of the head access window, and when the cartridge is in use this opening is positioned over the head access window to expose the magnetic recording media, and when the cartridge is not in use the opening is in a position of non-alignment with the window, so that the window is covered by the surface of the shutter. The shutter is provided with an engaging member which has a notch portion for engaging with an engaging portion of a torsion spring provided in the casing, and when the cartridge is not in use the force of the torsion spring pressing on the shutter keeps it in the position where the opening is not in alignment with the head access window. When the cartridge is in use an external mechanism in which the cartridge is provided acts to bend the torsion spring and move the shutter to bring the opening into alignment over the head access window so as to enable the cartridge to be used. However, in fitting the shutter to the cartridge, the notch portion thereof has to engage with the engaging portion of the torsion spring. Therefore, the engaging portion of the torsion spring has to have the same orientation as the axis of rotation of the magnetic recording media, and the surface of the engaging member of the shutter which comes into contact with the engaging portion acts to guide the engaging portion into the position of engagement in the notch portion. However, because the conventional guide portion forms a flat plane which is perpendicular with reference to the direction of sliding movement of the shutter, there is a large amount of resistance which makes it difficult for the engaging portion of the torsion spring to be guided securely into the notch portion, and there is even a risk of the engaging portion being deflected into the empty space on the opposite side to the notch portion. Also, it sometimes happens that the press-forming process imparts a slight projection or outward curvature to the guide portion, and this has made the said deflection more likely to occur. Because it is difficult to return a spring thus deflected to its correct position, such deflection has had a direct affect on the product yield. In assembly operations using the above construction, the rate of such faulty spring location is about 0.3%.